import java.util.Scanner;

/**
 * @author zhaoqian
 * @create 2021/8/30 14:57
 */
public class qiu {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            int str = in.nextInt();
            System.out.println(test(str));
        }
    }
    public static Double test(int hight){
        double hi=0d;
        double g=0d;
        g=(double) hight/2/2/2/2/2;
        hi=g*(4+8+16+32+32);
        System.out.println(hi);
        return g;
    }
}
